Broadcast transmission system



July 20,1926. l 1,592,885

C. H. FETTER BROADCAST TRANSMISSION SYSTEM Filed NOV, 5, 1925 @inkl Coil 1l ATTORNEY the lines L2 and L, together with the side band frequencies. As statedf,hereinbefore, the oscillations of the carrier frequency which are impressed by the winding l--l upon lthe windings 11 and'12 will not flow over the circuit 14 into the output side of the ower amplifier 4 because of the balanced l'condition of the windings 1l and 1'2 produced by the equal impcdances L2 and L.,

Itwill accordingly be seen that by eliminating the carrier frequencyfrom the power amplifier 4, the an'iplifyin'g power of this .device is utilizedpsolely in raising the side band 'frequencies to the required level for transmission over the lines L.: and Lp It will furthermore be seen that by employing a balance hybrid coil, the effect of the power oscillator upon the output side of the amplifier 'd is eliminated. IFurthermore the employment of one distributing Acircuit to balancethe other results in `the complete utilization ofthe output energy of the sys'- tem instead of distributing only one-half of it, as occurs 1n a system in which the distributing circuit is balanced by an artificial network.

While this invention has been disclosed as embodied schematically in a particular form, it is, of course, to be understood that the invention is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims.

What is claimed is:

' 1. In a broadcast system the method which consists in modulating a carrier by a signal frequency, selecting one of the side bands, transmitting this over a plurality of cir- `cuits, and simultaneously applying the carrier to said circuits in such manner that it will not react upon the side band translating circuit.v

2.1 In a broadcast system the method which consists in modulating a carrier by a signal frequency, selecting one of the side bands,

amplifying the said side band and f transmitting it over a plurality of circuits, and applying the carrier to the said circuits in such manner that it `vill not react upon the 'side bandtranslating circuit.

3. In a broadcast system, the mcthot which consists in generating a carrier fre--v quency current, modulating a portion of said current by a signal frequency, selectL ing one of the side bands resulting from such modulation, amplifying the selected 'side band to the'degree required for tansmission, transmitting it over a plurality of circuits, andapplying the remainder of said carrier frequency current to said plurality of circuits in such mannel as not to react upon the side band translating circuit.

4. In a broadcast system, the combination with a modulator ot a source of signaling voltage, a source of carrier voltage connect.

ed with said modulator, means to select 011e of the side bands produced by said modulator and to suppress other frequencies,

means to amplify the selected side bands, a plurality of transmission circuits, and means 'to connect thesaid amplifying means and the said source'of carrier voltage to said transmission circuits, the said connectingv hybrid coil connecting-said amplifier vwithA said transmission circuits and a power oscillator producing a carrier voltage connected with said modulator and with said hybrid coil in such manner as to prevent reaction of said carrier voltage upon the power amplifier.

6. In a broadcast system, the combination with a balanced modulator in which the carrier frequency is suppressed of a source of signaling voltage, a power amplifier, a single side. band 'filter connecting said modulator with said amplifier, a yplurality of t'ansmission circuits, a hybrid coil connecting said amplifier' with said transmission circuits, a power oscillator producing a carrier frequency connected with said modulator and with said hybrid coil, and means to control the amount of carrier energy applied to said modulator.

7 In a broadcast system, the combination with apluralityof lines over which material is to be broadcast, of a source of said material, the said source comprising a side band production circuit, a source of carrier current and a hybrid coil connecting said circuit and said source with the said lines, one-half of the group of said lines balancing the other half with respect to said circuit and said source, so that the entire energy of said circuit. and of said source is applied to said lines.

S. In a broadcast system, the combination with a broadcast production. circuit of a plurality of lines over which a side band is to be broadcast, a source oi' production of carrier current also to be distributed lo the 'said lines and means connectingthe said lilies with the said broadcast production circuit and said source of carrier current in such way that the full energy of the broadcast production circuit and the source of carrier currentwill be applied to said lines without causing interference lbetween said circuit and said source.

In testimony whereof, I have signed my naine to this specification this 2nd day fof November 199.5.

CHARLES H; WETTER. 

